The present invention relates to oil well production and relates in particular to a novel union structure between lengths of well production casing, tubing or drill pipe.
Prior art unions or connections between lengths of tubing frequently involve internal offsets or steps which result in a discontinuity in the interior wall of the tubing. Such an obstruction creates a choke or throttling effect restricting the flow of fluid materials pumped through the tubing.
This restriction results in turbulence which generates corrosion and erosion problems leading to weakening the union and thus creating a weak link in production tubing or drill pipe, as the case may be.
The problem is magnified when the fluid flowing through the tubing contains sand or other finely divided abrasive material.
In some prior art arrangements, the erosion problem is solved by introducing an inner tubular liner of high quality, erosion resistant metal wherein the liner segments abut one another to provide a straight through unobstructed flow path.
U.S. Pat. No. 4,568,113, issued Feb. 4, 1986 to Axford et al., is representative of these prior art structures.